This project is a pilot study to characterize the development and natural history of osteonecrosis (death of the bone tissue) in renal transplant recipients and determine associated epidemiologic and clinical risk factors. In addition, the feasibility of studying a larger patient population will be determined. Fifty adult recipients of first-time renal allografts, whose standard immunosuppressive regimen includes long-term glucocorticoids, will be prospectively monitored for development of ON and changes in bon mass and metabolism in the early post-transplant interval. Glucocorticoid dose, markers of bone turnover (NTX, osteocalcin), metabolic disease (PTH, calcitriol), BMD of the lumbar spine and hip, radiographs and MRI of the femoral head for ON, and responses to quality-of-life questionnaires will be examined at transplantation and at 6 months. Patients with On at 6 months will undergo repeat MRI at 18 months post-transplant.